Ratchet and pawl mechanism



Patented Dec. 30, 1941 2,268,243 I RATCHET AND PAWL MECHANISM John C.Curtis, Claremont, N. H., assignor to` Sullivan Machinery Company, a,corporation of' Massachusetts Application August 2, 1940, serial No.349,507

ZIClaims. (Cl. 'I4-,577) y This invention relates` `to ratchet and pawlmechanisms and more particularly to ratchet and `pawl mechanisms ofthetype adapted especially for use in hammerlrock drills. v A

It is an-object'of this invention to provide an improved ratchet andpawl mechanism. Another `object is to provide in a ratchet and `pawlmechanism of the type adapted for use in hammer rock drills, improvedmeansfor locking the pawls against inadvertent release with respect tothe `pawl carrier. Still another object isto provide an improved ratchetand pawl mechanism in which the pawls are locked against inadvertentrelease from the lpawl carrier irrespective of their supported positionbut may be released when desired. It is still ,another object to providea ratchet and pawl mechanism having improved means for con- "tinuouslyurging the pawlsintoengagement with the ratchet and `for locking thepawls against inadvertent release from the pawl carrier. Another objectis to provide inaratchet and pawl mechanism an improved spring pressedplunger engaging a pawl at points cl'osely adjacent to the axis of theplunger for urging the pawl into engagement with the ratchet, saidplunger having formed thereon meansA for locking the pawl againstinadvertent release from the pawl carrier. Still another object is toprovide an improved spring pressed plunger for a ratchet and pawlmechanism movable to different positions for presenting diierentportions to the pawl for wear.

Other objects and` advantages of the invention will, however,hereinafter more fully appear.

Inthe accompanying drawing there are shown for` purposes of illustrationtwo forms which the invention may assume in practice.

In this drawing:. I

Fig. l is a view mainly in longitudinal vertical section, but with partsin elevation, showing `a hammer rock drill in which an illustrativeembodiment of the invention is incorporated.

Fig.` is a side elevational View of one of the pawls.

Fig.` 6` is a perspective view of the pawl shown in Fig. 5.

Fig. 7 is a side elevational view of one of the 'spring pressedplungers.

Fig. `8 is a View taken on the plane of the line 8-8 of Fig. 7. l

Fig. 9 is a side elevational view of the plunger shown in Fig. '7 turnedthrough 90".l

Fig.v 10 is a side elevational View of a modied I form` of springpressed plunger.

In this illustrative embodiment of the invention there is shown a`hammer type rock drill, generally designated I, having a cylinder 2that isvprovided with a bore 3 within which a piston 4 is reciprocablycontained. Formed on the forward end of the piston is an elongatedstriking bar 5 of reduced cross section that is reciprocably guided in abushing 1 mounted in a front cyl- I inder head 8 for delivering impactblows to the shank of a drill steel. Formed in the striking bar arestraight grooves 9 slidingly interlocked with straight keys I0 on achuck member I| for transmitting rotary motion of the piston to thedrill Steel in the usual manner. Reciprocations mounted for rotationwithin a rear cylinder head I1 and a rear head block I8. Formedintegrally with `the rifle bar I6 adjacent its rear end is a pawlcarrier I9 which carries two pairs of pawls ,2I, 2| and 22, `22. Thepawlsare symmetrical in end elevation and in outline in side elevationand r cooperate with teeth `23 of a ratchet ring 24 which is threadedwithin the rear` head block I8. The pawls 2| and 22 `are suitablypivotally supported in sockets 26 and 2l respectively in the pawlcarrier I9, these `sockets being generally cylindrical I and openinginto spaces 28 formed bythe cutting away of the periphery of the pawlcarrier. The spaces 28 are so formed as to permit` the. pawls to swingoutwardly a suiicient `distance to `engage fully the ratchet teeth 23,but to restrain them from excessive outward movement.` To maintain thepawls in yieldingengagement withthe ratchet teeth 23, pawl-engagingplungers 30 are provided, these plungers being disposed in bores 3|extending chordally of the pawl carrier and being pressed yieldinglyagainst the inner surfaces of the pawls by springs 32. Two of the bores,3Ia, 3Ia, are herein arranged to the rear of the median transverse planeof the pawl carrier; the other two, 3| b, 3| b, are arranged forwardlyof that plane. The bores 3|a, 3Ia are parallel to each other, as are thebores 31D, 3|b; and the bores 31a, 31a are perpendicular to linesparallel to the bores Sib, 3Ib.

Each of the pawls comprises a blade portion r34 engageable with theteeth 23 of the ratchet and a pivot portion 35 pivotally seated in oneof the sockets 26 and 21. An opening 31 extends completely through theblade portion of each pawl at a point shown herein as positioned betweenthe center and one end of the pawl and close to the pivot portion 35.Since the pawls are symmetrical in shape they may be released from theirsockets and turned end for "e'nd and be reinserted within otherYsoclr'ets to present other portions of the pawls ifor 4engagement vwiththe ratchet teeth after the iirst pawl engaging portion becomes worn.

In order toimpart to each pawl a substantially constant pressurethroughout its full swing for urging it into engagement With the ratchetteeth, and in order to obtain contact between 1 the plunger and the pawlat pointswhich would prevent `a binding of theplunger in its bore andwhich would increasethe effective swinging force of the pawl, theplunger is cut away adjacent the pivottportion 35 of theipawl as a't 38kto provide shoulders 39 on the plunger for engaging the blade of thepawl. VThe plunger is cut back at 38 a suflicient distance to preventengagement of the plunger with the pawl, even when the plunger movesoutwardly to force the pawl into full engagement with a ratchet tooth,at points lbetween the engagement of the shoulders 39 with the pawl andthe inner end of the VpawL Ihe arrangement of the pawl and its plungeris such that when the pawl rides over 'the points of the ratchet teeth,the side of the pawl blade next to the plunger is at such an angle thattherel is only an engagement between the plunger and `the 'pawl at theshoulders 39 alongthe edgewhere theplunger is cut back. Formed on eachplunger atits end engaging the pawl is a reduced axial "projection 40extending within an opening 3l in a pawl :for positively locking vthepawl in Iposition on the' pawl carrier. In order that the 'plungers maybe inserted into or removed from within their bores when the pawls areremoved from the pawl carrier, there `are provided grooves 4| in thepawl carrier in alinement with the inner walls of the plunger bores. Y,

A modied form of plunger 43 is shown'inFig. 10, and is likethe plunger30 except that it is cut away at opposite sides, as at 44 `and'l5,V toprovide shoulders 46 providing two edges '41 and d8.` When one of theedges'becomes worn down the plunger maybe rotatedthrough 180 to bringtheother edge into position for engaging a pawl.v

'From the foregoingdescription, it Ywill be noted thatthere is providedVan improved ratchet and pawljmechanism in which the effective force ofthe spring-pressed plungers for urging 'the pawls 'intoengagement withthe ratchet teeth is maintained uniform and is applied at Ypoints lyingclose toa plane including the axis of the plunger. It will further benoted that thereis provided rneans for locking the pawls againstaccidental .removal while permitting swinging movement of the pawlsabout their `pivot axes on the pawl carrier. It will also be noted thatthe pawls are reversible to provide different portions which aresubjected to wear for engaging the ratchet teeth, and thatspring-pressed plungers are provided each having a plurality of pawlengaging portions selectively engageable with a pawl to distribute thewear. The structure is simple, of rugged construction, andjwell adaptedfor its intended purpose.

While there are in this application specifically described two formswhich the invention may assume in practice, it will be understood thatthese `forms vof the same are shown for purposes of 'illustration'l andthat the invention may be modi'ed `and embodied in various other formswithout departing Afrom its spirit or the scope of the appended claims.

What I claim as new and desire to secure by Letters Patent is: Y

1. In a ratchet and pawl mechanism, in cornbination, relativelyrotatable ratchet and pawl carrier elements. pawls pivotally mounted onsaid pawl carrier element and engageable with the teeth of said ratchetelement, said pawls having generally cylindrical pivot portions andprojecting blade portions, said blade portions engaging Y ...pointslying in the case of each plunger and the pawl with which it isassociated in a plane eX- tending transversely-of said pawl and in closeparallelism with the axis of said plunger.

` 2. In a ratchet landpawl mechanism, in combination, relativelyrotatable ratchet and pawl carrier elements, pawls pivotally mounted onsaid pawl carrier element and engageable with the` teeth of said ratchetelement, and plungers mounted on said pawl carrier element andrespectively yieldingly pressed into engagement with said.{pawls betweenthe ends of the latter for .yieldingly urging said pawls 4intoengagement with the ratchetteeth, said plungers having reduced lockingprojections extending lengthwiseof the axes of said plungers and saidpawls hav- `ing openings extending therethrough and within whichsaidlocking projections project, the pivotal mountings for saidrpawlsbeing so arranged that the faces of said pawls4 adjacent theirassociated plungers are spaced' over 90. from the axes of saidplungersin all positions of the pawls While engaging the ratchet-teeth, and saidplungers being cut away for limiting contact between each plunger andthe associated pawl, during engagement ofthe latter 'with the ratchetteeth, Y 1

topoints lying ,in a planeextending transversely of "said pawl and invclose parallelism with the axis of said plunger. Y

JOHN C. CURTIS.

